Strong spin-orbit splitting on Bi surfaces

Using first-principles calculations and angle-resolved photoemission, we show that the spin-orbit interaction leads to a strong splitting of the surface state bands on low-index surfaces of Bi. The dispersion of the states and the corresponding Fermi surfaces are profoundly modified in the whole surface Brillouin zone. We discuss the implications of these findings with respect to a proposed surface charge density wave on Bi(111) as well as to the surface screening, surface spin-density waves, electron (hole) dynamics in surface states, and to possible applications to the spintronics.Comment: 4 pages 2 figure

The role of the spin in quasiparticle interference

Quasiparticle interference patterns measured by scanning tunneling microscopy (STM) can be used to study the local electronic structure of metal surfaces and high temperature superconductors. Here, we show that even in non-magnetic systems the spin of the quasiparticles can have a profound effect on the interference patterns. On Bi(110), where the surface state bands are not spin-degenerate, the patterns are not related to the dispersion of the electronic states in a simple way. In fact, the features which are expected for the spin-independent situation are absent and the observed interference patterns can only be interpreted by taking spin-conserving scattering events into account.Comment: 4 pages, 2 figure

Spin-orbit induced interference in quantum corrals

Lack of inversion symmetry at a metallic surface can lead to an observable spin-orbit interaction. For certain metal surfaces, such as the Au(111) surface, the experimentally observed spin-orbit coupling results in spin rotation lengths on the order of tens of nanometers, which is the typical length scale associated with quantum corral structures formed on metal surfaces. In this work, multiple scattering theory is used to calculate the local density of states (LDOS) of quantum corral structures comprised of nonmagnetic adatoms in the presence of spin-orbit coupling. Contrary to previous theoretical predictions, spin-orbit coupling induced modulations are observed in the theoretical LDOS, which should be observable using scanning tunneling microscopy.Comment: 7 pages, 3 figures, accepted to Nano Letter

Ab initio electronic structure of thallium-based topological insulators

We analyze the crystal and electronic structures of T1-based strong topological insulators T1SbTe(2), T1SbSe(2), T1BiTe(2), and T1BiSe(2) by using first-principles calculation results. The topological nature of these materials is characterized by a single Dirac cone at the Gamma point. Aside from the latter robust surface state (SS), we find trivial SSs at (around) the Fermi level for large momenta as well as deep trivial SSs at (around) Gamma. The calculated energy cuts show an isotropic shape of the Dirac cone and a simple spin structure of the cone. The strong dependence of electronic structure on both optimization of the chalcogenide atom position in bulk and surface relaxations, as well as the slow convergence of the Dirac cone with respect to the film thickness, are discussed. The situation in the thallides is contrasted with results for isostructural indium compounds InBiTe2 and InSbTe2, the latter not being topological insulators

Surface- and edge-states in ultrathin Bi–Sb films

13 páginas, 7 figuras.Employing first-principles calculations, we studied the electronic structure of ultrathin Bi–Sb films, focusing on the appearance of surface or edge states that are topologically protected. Our calculations show that in ordered structures the Bi–Sb bonds are quite strong, forming well-defined double layers that contain both elements.We find surface states appearing on the (111) surface of a thin film of layerwise ordered Bi–Sb compound, while thin films in (110) orientation are insulating. In the gap of this insulator, edge states can be found in a (110)-oriented ribbon in the A17 (black phosphorus) structure. While these states are strongly spin polarized, their topological properties are found to be trivial. In all structures, we investigate the influence of spin–orbit coupling and analyze spin polarization of the states at the boundaries of the material.The financial support of the Deutsche Forschungsgemeinschaft (grant no. BI823/1-1).Peer reviewe

Surface electronic structure of Ti-based transition metal alloys

The electronic structure of the (001) and (110) surfaces for B2 Ti-based transition metal alloys were investigated using the full-potential linearized augmented plane-wave method in the local-density approximation. The evolution of the electronic structure of alloys at the different surfaces in comparison with the bulk ground states is analyzed. The ferromagnetic order is displayed in the case of Fe or Co top layer for the (001) surface. The surface magnetic moment of Fe and Co (2.27 mu(B) and 0.87 mu(B)) reduces drastically inside the film. The influence of a surface on the electron properties of alloys is discussedclose01